Quantitative characterization of colloidal assembly of graphene oxide-silver nanoparticle hybrids using aerosol differential mobility-coupled mass analyses.

In this work, we develop an aerosol-based, time-resolved ion mobility-coupled mass characterization method to investigate colloidal assembly of graphene oxide (GO)-silver nanoparticle (AgNP) hybrid nanostructure on a quantitative basis. Transmission electron microscopy (TEM) and zeta potential (ZP) analysis were used to provide visual information and elemental-based particle size distributions, respectively. Results clearly show a successful controlled assembly of GO-AgNP by electrostatic-directed heterogeneous aggregation between GO and bovine serum albumin (BSA)-functionalized AgNP under an acidic environment. Additionally, physical size, mass, and conformation (i.e., number of AgNP per nanohybrid) of GO-AgNP were shown to be proportional to the number concentration ratio of AgNP to GO (R) and the selected electrical mobility diameter. An analysis of colloidal stability of GO-AgNP indicates that the stability increased with its absolute ZP, which was dependent on R and environmental pH. The work presented here provides a proof of concept for systematically synthesizing hybrid colloidal nanomaterials through the tuning of surface chemistry in aqueous phase with the ability in quantitative characterization. Graphical Abstract Colloidal assembly of graphene oxide-silver nanoparticle hybrids characterized by aerosol differential mobility-coupled mass analyses.

Metal-Organic Framework Colloids: Disassembly and Deaggregation.

We demonstrate a high-resolution method as an efficient tool to in situ characterize partially reversible assembly and aggregation of metal-organic framework (MOF) colloids. Based on the gas-phase electrophoresis, the primary size and the degree of aggregation of the MOF-525 crystals are tunable by pH adjustment and mobility selection. These findings allow for the further size control of MOF colloids and prove the capability of semiquantitative analysis for the MOF-based platforms in a variety of aqueous formulations (e.g., biomedical applications).

Quantifying nanosheet graphene oxide using electrospray-differential mobility analysis.

We report a high-resolution, traceable method to quantify number concentrations and dimensional properties of nanosheet graphene oxide (N-GO) colloids using electrospray-differential mobility analysis (ES-DMA). Transmission electron microscopy (TEM) was employed orthogonally to provide complementary data and imagery of N-GOs. Results show that the equivalent mobility sizes, size distributions, and number concentrations of N-GOs were able to be successfully measured by ES-DMA. Colloidal stability and filtration efficiency of N-GOs were shown to be effectively characterized based on the change of size distributions and number concentrations. Through the use of an analytical model, the DMA data were able to be converted into lateral size distributions, showing the average lateral size of N-GOs was ∼32 nm with an estimated thickness ∼0.8 nm. This prototype study demonstrates the proof of concept of using ES-DMA to quantitatively characterize N-GOs and provides traceability for applications involving the formulation of N-GOs.

Thermal Stability of Metal-Organic Frameworks and Encapsulation of CuO Nanocrystals for Highly Active Catalysis.

We report an aerosol-based approach to study the thermal stability of metal-organic frameworks (MOFs) for gas-phase synthesis of MOF-based hybrid nanostructures used for highly active catalysis. Temperature-programmed electrospray-differential mobility analysis (TP-ES-DMA) provides the characterization of temperature-dependent morphological change directly in the gas phase, and the results are shown to be highly correlated with the structural thermal stability of MOFs determined by the traditional measurements of porosity and crystallinity. The results show that MOFs underwent thermal decomposition via simultaneous disassembly and deaggregation. Trimeric Cr-based MIL-88B-NH2 exhibited a higher temperature of decomposition ( Td), 350 °C, than trimeric Fe-based MIL-88B-NH2, 250 °C. For UiO-66, a significant decrease of Td by ≈100 °C was observed by using amine-functionalized ligands in the MOF structure. Copper oxide nanocrystals were successfully encapsulated in the UiO-66 crystal (Cu xO@UiO-66) by using a gas-phase evaporation-induced self-assembly approach followed by a suitable thermal treatment below Td (i.e., determined by TP-ES-DMA). Cu xO@UiO-66 demonstrated a very high catalytic activity and stability to CO oxidation, showing at least a 3-time increase in CO conversion compared to the bare CuO nanoparticle samples. The study demonstrates a prototype methodology (1) to determine structural thermal stability of MOFs using a gas-phase electrophoretic method (TP-ES-DMA) and (2) to gas-phase synthesize CuO nanocrystals encapsulated in MOFs.

Photostable BODIPY-based molecule with simultaneous type I and type II photosensitization for selective photodynamic cancer therapy.

We introduce a new class of photostable, efficient photosensitizers based on boron-dipyrromethene (BODIPY) derivatives that can generate singlet oxygen and superoxide simultaneously under irradiation. First, we report the synthesis and design of how to control the generation of a specifically substituted position of BODIPY. Second, after biologically evaluating the uptake, localization and phototoxicity in cell lines, we conclude that 2,6-di-anisole substituted BODIPY is a potentially selective photodynamic therapy candidate because its photodamage is more efficient in cancer cells than in normal cells without significant dark toxicity.

Special reactive oxygen species generation by a highly photostable BODIPY-based photosensitizer for selective photodynamic therapy.

We introduce a new class of photostable, efficient photosensitizers based on boron-dipyrromethene (BODIPY) derivatives that can generate singlet oxygen and super oxide simultaneously under irradiation. For compound preparation, appropriate regulation of the reaction conditions and control of specifically substituted BODIPY derivatives have been achieved. After biologically evaluating the intracellular uptake, localization, and phototoxicity of the compounds, we conclude that 3,5-dianiline-substituted BODIPY is a potentially selective photodynamic therapy candidate because its photodamage is more efficient in cancer cells than in normal cells, without apparent dark toxicity. Furthermore, direct comparison of photodamage efficacy revealed that our compound has better efficacy than Foscan and nearly equal efficacy to that of methylene blue.